Nickel base alloys and electrical resistance wire made therefrom



United States Patent 3,406,058 NICKEL BASE ALLOYS AND ELECTRICALRESISTANCE WIRE MADE THEREFROM Stephen Poch, Wyckolf, Edward E. Edmunds,Shrewsbury,

and Arthur S. Lichter, Allenwood, N.J., assignors to Molecu-WireCorporation, a corporation of New Jersey No Drawing. Filed July 11,1966, Ser. No. 564,020

7 Claims. (Cl. 75-171) ABSTRACT OF THE DISCLOSURE A nickel base alloywith a flat temperature coefiicient of resistivity and the manufactureof wire products from said alloy.

Preferred Minimum Maximum Chromium 17. 22. 5 19. 5-21 Manganese. 4. 5 5.5 About 5 Aluminum 4 4. 5 About 4.3 Silicon.-- 0. 90 1. 25 About 1.1Nickel 1 Balance 1 Balance 1 Balance 1 Except for minor amounts of andimpurities incidental to the type of 80/20 Ni-Cr alloy.

trace elements, deoxidizers, degasifiers, normal commercial productionof this It also relates to an extremely rapid heat treatment of suchalloys at temperatures in the range of 1200 F. to 1900 F. for unusuallyshort time intervals, usually less than five seconds. This heattreatment being eifected preferably immediately after the alloys havebeen fabricated into wire by combinations of hot working and coldworking and prior to incorporation into a finished article ofmanufacture, such as a potentiometer, wire wound resistor, or otherelectrical and electronic apparatus.

One object of the invention is the production of alloys from which wirewith desirably low coeflicients of resistivity and desirably highelectrical resistances is reproducibly obtained.

A principal object of the invention is the production of a wire producthaving an unusually fiat temperature-resistance curve over the range ofminus 55 C. to plus 150 C.

Another object is to provide a wire product having a controlledtemperature coefiicient of resistance which may be positive, ornegative, or zero according to the specific processing to which the wireis subjected.

Still a further object is to provide an alloy which may be formed intowire having a combination of high resistance, low temperaturecoefiicient of resistance, improved stability and uniformity of therelation between resistance and temperature.

A further object of the invention is to provide an unusually brief heattreatment for the improvement of wire produced from said alloys.

These and other objects will be apparent from the more completedisclosure of preferred aspects of this invention which follows.

As noted in United States Patent 2,996,378, issued Aug. 15, 1961,nickel-chromium alloys of the 80/20 type, modi fied by the addition ofAl and other specific elements, are well known and have been extensivelyinvestigated.

3,406,058 Patented Oct. 15, 1968 The present invention consists in theuse of the above noted combination of alloying elements Within the verynarrow ranges of proportions specified, to produce stable products withspecific resistances of at least as high as 860 ohms per circular milfoot and temperature coefiicients of resistance of less than about onepart per million over a temperature range of minus 55 C. to plus C. arereadily and reproducibly obtained.

In the alloys of this invention the specific range of chromium contentis less critical than the ranges specified for the remaining alloyingelements and amounts as low as 15 weight percent and as high as 25weight percent may be tolerated without sacrificing the benefitsconferred by the presence of aluminum, manganese and silicon in theproper proportions. However, a chromium content in the range of betweenabout 20% and 21% by weight is preferred.

The manganese content of the alloys of this invention appears to beparticularly important, because when the manganese exceeds about 5.5% byweight the alloys are extremely diflicult to hot work and tend to edgecrack excessively and when the manganese is below about 4.5% thestability and temperature coeflicient of resistance are adverselyaffected and more extensive heat treatment is required to develop thedesired properties, than when the manganese is in the range of aboveabout 4.5 and up to about 5.5% by weight.

The presence of aluminum in amounts greater than 4% also appears topermit greatly simplified and shortened heat treatments as compared withthe prior art alloys in this field.

One important difference between the alloy of this invention and priorart alloys is in the presence of about 1% silicon which is many timesthe amount of silicon required for simple deoxidation and degasificationof the alloy. The presence of this increased amount of silicon alsoappears to permit processing by greatly accelerated heat treatmentswithout loss of the desired properties.

Preferred alloys in accordance with this invention are those containingbetween about 19.5% and 21% Cr; from about 4% to 4.5% A1; from about4.5% to 5.5% Mn; from about 0.9 to 1.25% silicon; not more than 0.5% Cu;not more than 0.9% Fe; a maximum of about 0.03% C; less than 0.005% of Por S; the balance nickel except for minor amounts of deoxidizers anddegasifiers, such as Zr, Ti and the like, totalling less than about0.3%.

The following alloys will further illustrate the present invention(percent by weight):

hibited a temperature coefficient of resistance of less than one partper million over the temperature range of minus 55 C. to plus 125 C. aswell as a nominal resistivity of at least 860 ohms per circular milfoot, whereas alloy No. 5 with the higher manganese disintegrated duringhot working and alloy No. 1 with a manganese content below the desirerange exhibited a temperature coeiiicient of resistance of between 3 and5 parts per million (with 25 C. as the reference temperature) over therange minus 55 C. to plus 125 C. which is very little improvement overthe prior art.

The following is a description of one manner in which 3 alloy No. 3(above), containing .004% S, 001% P and 0.77% Fe as impurities, has beenworked, omitting conventional coating, cleaning, pickling, incidental towiredrawing.

(1) Hot work to /1" rod.

(2) Anneal at 2100 F.

(3) Rapidly quench.

(4) Draw successively to the following diameters, annealing thecontinuous strand at 2100 F. after each draw: .140"; 0.080" and 0.032".

(5 Draw to .0142" diameter; .004 diameter and then .001 diameter orother desired final diameter.

(6) Anneal in gradient furnace with nonoxidizing atmosphere such ascracked ammonia.

The final annealing temperature depends in part on the size of the wirebeing processed, the speed at which it passes through the furnace andthe temperature coefiicient desired. Annealing temperatures between 1200F. and 2100 F. are usually employed at this stage of the process, fortimes of between two and fifteen seconds.

Having now described the invention it is not intended that it be limitedexcept as may be required by the appended claims.

We claim:

1. A nickel base alloy consisting essentially of between about 15 and25% Cr, between about 4.5 and 5.5% Mn, between about 4 and 4.5% A1,between about 0.90 and 1.25% Si, balance nickel except for incidentalimpurities.

2. An electrical resistance wire formed. of the alloy of claim 1.

3. An electrical resistance wire alloy having a fiat temperaturecoefiicient of resistance characteristic and consisting essentially ofthe alloy of claim 1.

4. A nickel base alloy consisting essentially of the following inpercent by weight:

balance nickel except for incidental impurities.

5. The alloy of claim 4 wherein the chromium content is between 20 and21% by weight.

6. The alloy of claim 5 wherein the manganese is about 5%, the aluminumis about 4.3% and the silicon is about 1.1%.

7. In a method of processing a nickel base alloy consisting essentiallyof between about 15 and 25% Cr, between about 4.5 and 5.5% Mn, betweenabout 4 and 4.5% A1, between about 0.90-and 1.25 Si, balance nickelexcept for incidental impurities, according to claim 1, to produce awire product having a desired temperature coeflicient of resistivity,which alloy has been Worked and heat treated to produce a wire of thedesired final dimensions, the improvement in combination therewith whichcomprises final annealing said alloy between 2 and 15 seconds at atemperature of between 1200 F. and 2100 F.

References Cited UNITED STATES PATENTS 2,460,590 2/ 1949 Lohr -1712,533,735 12/1950 Lohr 75-17l 2,533,736 12/1950 Lohr 75-171 2,996,3788/1961 Edmunds et al. 75171 RICHARD O. DEAN, Primary Examiner.

